Simplify file handling - unify handling input/output streams and regular files

[carbolymer]

As a result of #5016 , one can use stdout and stdin as output and input streams respectively using - as a CLI file name argument. This gets handled in code as Maybe FilePath which is not very intuitive to use.

The goal of this issue is to replace Maybe FilePath with a datatype unifying handling of stdout /stderr and regular files.

Depends on:

• https://github.com/input-output-hk/cardano-node/pull/5049/files
• [FR] - All command line options that take a filename should also take "-" #5016

[github-actions]

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